The present invention relates to a coupling structure for a tube which is used, for example, at the time of burying a cable such as a wire cable in the ground, for attaching a protection tube used for protecting the cable to a hand hole made of concrete, and also includes a coupling structure for a tube used for coupling various types of tubes.
Conventionally, as a means for attaching a cable protection tube made of composite resin to a hand hole, there is provided such an arrangement shown in FIG. 13 that a through hole 52 is provided at the side wall 51 of the hand hole made of concrete which is provided in advance, then the tip end of a protection tube 53 is inserted into the through hole 52, and mortar 54 is filled into a space between the protection tube 53 and the through hole 52 to thereby fix the protection tube. A reference numeral 55 depicts a bellmouth attached to the tip end of the protection tube 53.
However, this method requires troublesome procedures such as the hole making procedure at a construction site, the filling procedure of mortar etc. Further, the next procedure can not be started until the mortar thus filled is hardened. In this manner, this method has a defect that the troublesome procedure and much time is required.
As a means for solving such a problem, Japanese Patent Examined Publication No. Sho. 60-14568 discloses such an arrangement that, at the time of providing a hand hole, a conduit opening member provided separately from a protection tube at the outer periphery thereof is buried in advance such that the end portion thereof protrudes on the outer side of the hand hole, and the protruded end portion is coupled with the end portion of the protection tube by using another joint tube. In this case, as each of the protection tube and the conduit opening member, a spiral corrugated tube with the same diameter having a spiral projection portion on the outer periphery thereof is employed. The joint tube engages with the protection tube and the conduit opening member so as to extend both of them by using the spiral projection portions thereof.
However, the method of the aforesaid publication also requires a procedure of screwing the joint tube into the protection tube and the conduit opening member. In this case, it is required to hold the protection tube and the conduit opening member so as to be arranged in a straight line during the screwing procedure. In particular, since the protection tube is very long and has been wound in a roll shape before installation, the protection tube likely holds its rolled shape, it is difficult to hold the protection tube and the conduit opening member in a straight shape.
Further, since the protection tube and the conduit opening member are coupled simply by means of the joint tube, there is a disadvantage that water in the ground likely enters into the gap therebetween.
Accordingly, an object of the invention is to provide a tube coupling structure which can eliminate the aforesaid conventional drawbacks, can perform simply in a short time a coupling procedure at the time of coupling tubes like a case of coupling a conduit opening member buried in a hand hole with a cable protection tube, and is excellent in watertightness.
In order to solve the aforesaid problem, the invention is characterized by including a come-out preventing member which is held at an outer periphery of a first tube member of a pair of tube members to be coupled to each other in a state being restricted in its movement in a longitudinal direction of the first tube member at a tip end portion on a coupling side of the first tube member, and an engaging member protruded from an end portion on a coupling side of a second tube member which is the other of the pair of tube members, wherein the come-out preventing member and the engaging member are respectively provided with engaging portions which act to engage the come-out preventing member and the engaging member to each other to prevent the first and second tube members from being separated to each other in a state where the come-out preventing member is pushed into the engaging member, and wherein at least one of the engaging portions has elasticity with respect to a radial direction of the tube member or elastically supported so that the engaging portions are placed in an engaged state to each other due to the elasticity of the at least one of the engaging portions when the come-out preventing member is pushed into the engaging member.
In the aforesaid arrangement, it is preferable to have an arrangement in which the engaging member is threadedly engaged with the second tube member so as to be separatable from the second tube member by rotating the engaging member relative to the second tube member while the engaging member and the come-out preventing member are being engaged to each other. With this arrangement, the coupling state between the first and second tube members can be easily released by the rotation thereof even after the coupling in the longitudinal direction.
In the above-mentioned structure, it is advantageous that a packing is provided which is housed in a packing housing portion of the second tube member in a state where the packing is fitted on an outer periphery of the tip end portion on the coupling side of the first tube member, and the come-out preventing member is attached to an inner side from the packing along the longitudinal direction of the first tube member.
In this case, it is further advantageous that the come-out preventing member abuts its tip end against an end surface of the packing to thereby support the packing from a rear portion side thereof along a pushing direction when the packing is pushed within the housing portion.
Further, it is considered that the first tube member is a spiral corrugated tube having a spiral-shaped projection on the outer periphery thereof, and the spiral corrugated tube is arranged in a manner that the come-out preventing member meshes with the spiral-shaped projection to restrict movement or the come-out preventing member in the longitudinal direction of the tube member.
According to this, there is provided an arrangement that the engaging member is arranged in a manner that it is meshed with and attached to the end portion on the coupling side of the second tube member and separated from the end portion on the coupling side by releasing the meshed state.
Further, in the present invention, there may be provided an arrangement that the fist tube member is a cable protection tube for an electric wire cable etc. buried within ground, and the second tube member is a conduit opening member which is buried in a side wall of a hand hole made of concrete and serves to introduce the cable passed through the first tube member within the hand hole.
In this invention, the tube members include not only members generally called tubes but also other tubular members such as joint tubes.